The way I see it, what the PC does in Div 2 is changing the memory of Ygerna's soul, so that the soul no longer has any reason to be in the Hall of Echoes (since it no longer remembers that Ygerna died, as the PC rescued Ygerna in the memory) and returns to Ygerna's corpse (which is somehow not headless) in Damian's fortress in Rivellon.
